Tube Dampers, are they for real?

I keep seeing "Tube Dampers" for sale on ebay. Do these silicone rubber bands really make a difference in the "microphonics" of tubes, or are are they just another way for venders to separate us from our money. If there are any "tube sommelier's" out there that have tried these simple devices, I would sure like to hear your comments pro and con regarding them. The descriptive narratives give plausible reasons for using them and extol their virtues in their ability to improve tube sound. Are vibration from external sources really that much of an influence on tube sound quality?

I like to think that I have a discerning ear and am open to something new if it proves to be worthwhile.

Call me a skeptic, but I'd think that since the tube is in a vacuum inside, what's there to dampen? I could see it stopping the resonating of the glass maybe, and stopping the tube from "shaking", causing harmonics, like walking across a hard floor with your amp on a hard table surface might cause.

But I would think there are better solutions. Such as rubber feet or mat.

I use basic $1 each silicone dampers on the tubes in my linestage and my voltage amplifier and driver tubes on my amp. Do they do anything? Maybe. I believe that I've noticed a bit more focus and a tighter soundstage with them in place. It's perhaps more of what you don't notice, that is: the system sounds great with them in place, but if I remove them, I perceive a loss of sound quality and focus. I only started using them when Conrad Johnson started using them on factory amps. I figure they know what they're doing. I think the idea is the damper minimizes vibration on the glass envelope of the tube, therefor stopping that vibration from transferring to the inner plate and screen structures via the mica spacers (which contact the glass). I'll note that I haven't tried any of the expensive UFO looking dampers made by Herbie's or the EAT ones that are supposed to provide cooling as well. I figured $1 a tube was worth the experiment and so far I think I got my money's worth and then some.